21243776 has 64 divisors (see below), whose sum is σ = 44982000. Its totient is φ = 9977856.

The previous prime is 21243769. The next prime is 21243779. The reversal of 21243776 is 67734212.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243779) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 218960 + ... + 219056.

Almost surely, 2^21243776 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21243776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22491000).

21243776 is an abundant number, since it is smaller than the sum of its proper divisors (23738224).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21243776 is an equidigital number, since it uses as much as digits as its factorization.

21243776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199 (or 187 counting only the distinct ones).

The product of its digits is 14112, while the sum is 32.

The square root of 21243776 is about 4609.0970916222. The cubic root of 21243776 is about 276.9558679752.

Adding to 21243776 its reverse (67734212), we get a palindrome (88977988).

It can be divided in two parts, 2124 and 3776, that multiplied together give a square (8020224 = 2832²).

The spelling of 21243776 in words is "twenty-one million, two hundred forty-three thousand, seven hundred seventy-six".